The validity of simulated root canals for the investigation of the prepared root canal shape

Summary. Curved root canals from extracted human teeth were prepared using K‐type files. The resultant shapes were compared both quantitatively and qualitatively with canals that were formed in polyester clear casting resin and similarly prepared. Moderately curved canals generally demonstrated a funnel‐shaped canal preparation. Severely curved canals showed a high incidence of hour‐glass shaped preparations. When the proportions of the hour‐glass shaped canals from extracted teeth and simulated root canals were compared, there were no significant differences.